Electric switch



Patented Aug. 21, 1951 UNITED STATES PATENT OFFICE to The Western UnionTelegraph Company, New York, N. Y., a corporation of New YorkApplication June 29, 1948, Serial N 0. 35,928

3 Claims. 1

This invention relates to improvements in magnetically operatedswitches, and more particularly to such a switch which operates in avacuum or rarefied atmosphere.

A magnetically operated switch in which the circuit controlled therebyis made and broken between solid contacts in a vacuum is particularlysuitable for starting vapor and gas-filled discharge lamps or tubes,such as mercury vapor arc lamps and also concentrated arc dischargelamps of the character disclosed in Buckingham et al. application SerialNo. 668,092, filed May 8, 1946, now Patent No. 2,453,118, issuedNovember 9, 1948, and Buckingham application Serial No. 24,555, filedMay 1. 1948.

Among the objects of the invention are to provide a switch of thecharacter described which is more dependable in operation; which has agreatly increased life; and which may be made small and compact andembodies improved and simplified means for mounting the armature of theswitch.

Other objects and advantages will be apparent from the followingdetailed description of an illustrative embodiment of the invention,taken in connection with the accompanying drawings in which:

Fig. 1 is a front view, in elevation, of a vaculim switch embodying theprinciples of the inven- Fig. 2 is a side view of the switch of Fig. 1;

Fig. 3 shows the switch inserted in operating position within the coilof an electromagnet;

Fig. 4 is a cross-sectional view taken along the line 4-4 of Fig. 1,looking in the direction of the arrows;

Fig. 5 shows a modified form of the switch structure; and

Fig. 6 shows the switch employed in the starting circuit of aconcentrated are discharged lamp.

Referring to Figs. 1 and 2, the embodiment there illustrated comprises atubular sealed glass envelope l0 having a base I! of insulation withmetal contact prongs I 2 for insertion into a socket thereby to connectthe switch in the circuit which it is to control. In the figures theglass envelope I0 is shown as partially broken away in order to disclosebetter certain of the elements within. Connected to the prongs 12 aretwo lead-in conductors II which pass through and are supported by thepress 15 of the tube. Secured to the upper ends of the lead-inconductors M, as by soldering or welding, are small tungsten coils IS,the upper ends of which coils are bent, as seen in Fig. 1, to formflexible contact members adapted to be bridged by a switch element 18.

Extending upwardly from the press I6 is a wire 2! of molybdenum,nickeLor other suitable metal, and surrounding the wire is a glass orvitreous tube 22, the upper end of which passes through a central holein a disk 24 of mica or other suitable material. The circular edge ofthe disk 24 is in contact with the inner wall of the tube Ill so thatthe upper rod assembly 2|, 22 is firmly positioned centrally of the tubeonvelope.

As seen in Fig. 4, the bridging switch member l8 conveniently maycomprise a round washer, preferably of molybdenum, which is spot-weldedor otherwise secured to an armature in the form of a cylinder 26 of ironor other good magnetic material. The rod 2| and tube 22 provide alongitudinal supporting and guiding axis which passes through thecylinder 26 and washer l8 with a loose fit and along which the assemblyI8, 26 may freely slide and about which axis the assembly may freelyrotate as the switch is operated under the influence of an electromagnetshown in Fig. 3. The electromagnet comprises an inductive winding 30containing a sufficient number of ampere turns to produce a strongmagnetic field and cause quick operation of the armature 26; for usewith a small vacuum switch tube, two thousand turns of No. 30 magnetwire are satisfactory. I'he coil is wound on a sleeve 3| of brass orother non-magnetic material within which the tube l 0 is received, andthe ends of the electromagnet conveniently may comprise iron washers 32mounted on the brass sleeve 3|. When current is caused to flow throughthe winding 30 a magnetic field is set up which attracts the cylindricalarmature 26 and causes it and the bridging switch member I 8 to moveupwardly so that the circuit between the contact spring members l6 andthe bridging member 18 is quickly broken. The circuit is maintained openso long as the electromagnet 30 is energized. I

Since the armature 26 and contact member l8 are free to rotate abouttheir common axis this causes the bridging disk I 8 to present a newcontact surface from time to time to the spring contact members l6 andthus minimize pitting of the contact surfaces. Also, the ends of thespring contacts l6 may wear down and still make good contact with thedisk [8 and the flexibility of the springs insures that both will alwaysmake good contact with the bridging member even though the spring shouldwearv down unevenly. The tube or envelope [0 is evacuated to as high aderee as practicable in order to insure a rapid break, without arcing,in the current flowing through the switch contacts when the electro- 3magnet 30 is energized. Since the switch elements do not touch the glassenvelope they can readily be degassed by heating the same while the tubeis being exhausted.

When the tube is positioned within the sleeve 3| of the electromagnet,as shown in Fig. 3, the switch contacts Iii are closed when theelectromagnet is not energized and are opened when it is energized, butby inverting the tube within the sleeve the contacts may be caused toremain open when the electromagnet is deenergized and closed when it isenergized. Thus, the circuit controlled by the switch may normally bekept either open or closed, depending upon the character and purpose ofthe circuit.

Fig. 5 shows a modified form. of the switch structure in which thebridging contact member, viz., the molybdenum washer or disk I8, isloosely mounted on a neck portion 35 of the iron armature 26, which neckportion is peened over so that the disk can not come ofi, although it isloose so that it is floppy. In this modification the switch contacts maysimply comprise stubs M of wire, preferably molybdenum or nickel,without the spring tips shown in the first described form. The washerordisk l8 will align itself to take care of any difierence in height ofthe two contacts. The bevel 36 on the bottom of the armature assuresthat it will always press on the member I8 at its center. The couplethus formed with the disk touching one of the contacts l4 assures thatthe disk will touch the other contact also. The vertical play betweenthe armature 26' and disk l8 provides a hammer action which is useful inopening the contacts if they should tend to stick to the disk.

Fig. 6 shows a starting circuit for a concentrated arc lamp 40controlled by a vacuum switch constructed in accordance with the instantinvention. The lamp 4% is of the type in which two anodes M cooperatewith a common cathode 42, the lamp being operated from a source ofdirect current supply 45. Ballast resistors A6 are inserted in thepositiveside of the circuit to the anodes M. The electromagnet 39, whichalso comprises a choke coil, is connected to the oathode 42 forcontrolling the armature 26 of the vacuum switch, the circuit throughthe contacts 16 of the switch including a current limiting resistor 48.When starting the lamp, current through the coil 39 actuates thearmature 26 and causes the switch to open its contacts, and theinductive surge produced by the coil 30 due to operation of the vacuumswitch is impressed across the arc lamp, the condenser 58 readilypermitting the inductive'surge to be impressed upon the anode.

When the gas in the lamp becomes ionized, current flows through theballast resistors 46 in parallel so that the arc stream is dividedbetween the two anodes 4|, the return path from the cathode 42 includingthe coil 30 which attracts the armature 26 and maintains the vacuumswitch in open circuit position so long as the lamp is operated. Sincethe arc stream is divided between the anodes, only one-half of thecurrent flowing passes through each anode and the heating effect on eachanode is correspondingly decreased.

In addition to its use in the starting circuit of a vapor lamp or otherarc discharge device, the switch may be employed for controlling varioustypes of circuits in which it is desirable or necessary to open andclose a circuit between solid electrodes with a minimum of arcing andwithout any appreciable time delay in operation.

While there are shown and described herein certain preferred embodimentsof the invention, many other and varied forms and uses will presentthemselves to those versed in the art without departing from theinvention which, therefore, is not limited either in structure or useexcept as indicated by the scope of the appended claims.

We claim:

1. An electric switch comprising a sealed envelope having a pressportion, a pair of fixed contacts supported within said envelope by thepress portion, an armature of magnetizable material within the envelopemovable in one direc tion when subjected to an external magnetic fieldand movable in the opposite direction under the influence of gravity, abridging contact member carried by said armature and adapted to extendbetween and engage said fixed contacts the circuit-closing position ofthe switch, a fix ed rod extending through said armature and bridgingmember with a loose sliding flt andv providing a supporting and guidingaxis defining the-path of movement of the armature and bridging contactmember, and means including said press portion of the envelope and aspacer member engaging the inner wall of the envelope for mounting saidfixed rod.

2. An electric switch comprising a sealed envelope having a pressportion, a pair of fixed contacts within said envelope, an armature ofmagnetizable material within the envelope 1novable in one direction whensubjected to an ex-* ternal magnetic field and movable in the oppositedirection under the influence of gravity, a bridging contact membercarried by said armature and adapted to extend between and engage saidfixed contacts in the circuit-closing position of the switch, saidbridging member being loosely mounted on said armature-so as to befloppy whereby the bridging member will align itself to take care of anydifference in height of the fixed contacts relative to each other, afixed rod extending through said armature and bridging member with aloose sliding fit and providing a supporting and guiding axis definingthe pathof movement of the armature and bridging contact member, andmeans including said press portion of the envelope and a spacer memberengaging the inner wall of the envelope for mounting said fixed rod.

3. An electric switch comprising a sealed envelope having a pressportion, a pair of fixed contacts within said envelope, an armature ofmagnetizable material within the envelope movable in one direction whensubjected to an external magnetic field and movable in the oppositedirection under the influence of gravity, a bridging contact membercarried by said armature and adapted to extend between and engage saidfixed contacts in the circuit-closing position of the switch, a fixedrod extending through said armature and bridging member with a loosesliding fit and providing a supporting and guiding axis defining thepath of movement of the armature and bridging contact member, and meansincluding said press portion of the envelope and a spacer memberengaging the inner wall of the envelope for mounting said fixed rod,said spacer member being positioned along-the rod at a place to providea stop for the movement of the armature in one direction of its travel.

WILLIAM D. BUCKINGHAM. CONSTANCE J. BRUZDOSKI.

(R fer n s ollowing p e) REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 1,238,667 Halbleib et a1 Aug.28, 1917 1,783,279 Burnham Dec. 2, 1930 1,928,846 Allen Oct. 3, 19331,981,534 Wilms et a1 NOV. 20, 1934 10 Number Number Name Date Ronci etal. Apr. 22, 1935 Lear Aug. 5, 1947 FOREIGN PATENTS Country Date GreatBritain Oct. 2, 1929 Germany Dec. 10, 1924 Germany 1 Oct. 28, 1927France Sept. 29, 1941

